Is it permissible to use the serial number for computer programs published in Islamic forums, and is that considered theft from the producing company or a gift?

If the company reserves the right to donate its products exclusively to itself or its employees, then it is not permissible for others to infringe upon or dispose of this right. However, if the company does not reserve this right, or if it authorizes its employees to donate them to whomever they wish, then they may do so within the limits of the authorization.